A château in Texas might seem as oxymoronic as a ranch house in Normandy, but try on this cour d'honneur in Dallas for size: Two arms of a stately mansion in University Park make you feel elevated, even noble, as you step across the forecourt and walk down the axis of its symmetry, the object of its architectural attention. Grand without being 10-gallon about it, the limestone portal around the front door invites you into a central hall, where a sense of ceremonial procession ushers you through French doors into a living room luminous with an amber glow. The far wall is lined with French doors that open out onto the back 40, a terraced and hedged formal garden graced with swanning oaks.

Harmony and proportion pervade the house and its gardens, showing that classicism is at home even on the range. But an unexpected moment transcends the apparent propriety. The living room may feature a graceful second-century Roman statue of Venus that anchors the house in Greco-Roman tradition, but presiding over a sofa is a heroic Abstract Expressionist canvas by Joan Mitchell—an Armageddon of brushstrokes and color that shower the living room with energy. The painting throws the elegant, disciplined classicism a counterintuitive curve. Decorum here has attitude.

Nancy Cain Marcus, chatelaine of the house and a Ph.D. who teaches literature at the University of Dallas, was first introduced to the distinguished building as a girl by her mother on their drives through the city. Finished on the cusp of the Depression in 1929 and designed by the noted Revivalist architect John Scudder Adkins, the house was occupied by the same generation of the same family of American diplomats and industrialists who originally built it. "You walked in and knew someone had loved it," says Marcus. "And since the interiors literally had never been altered, no mistakes had been made." Nonetheless, the house, organized when there was a marked upstairs/downstairs split in the sociology of mansions, had to be brought into a post-Proustian era for a contemporary lifestyle. "It was time to refresh the house—it clearly needed vitality," she says. "Still, an obligation came with the property because it was an icon of an era in Dallas that stood for a certain order of civility and gentility."

Marcus researched her way to the New York office of Peter Marino, a high-voltage, fullservice architect who respects period styles and designs from the floor plan to the Ming vase, soup to nuts. "The house belonged to very good housing stock from the '20s and wasn't in any way a bad copy of a château," says Marino. "The proportions and layout were more American. We wanted to lighten and brighten it without changing its bones."

Classicized buildings, even in their American incarnation, embody changeless ideals, and today the house seems to have always been there in its present form. Standing in the entrance hall, however, Marcus points out that the first set of French doors and the checkered marble floor are, in fact, among the few parts of the original house left intact. Marino reworked the house completely inside, but without leaving behind any fingerprints. It's impossible to separate the new from the old. He changed everything and nothing. "I was really reassured that I was in the hands of an academic," says Marcus. "Peter takes the history of architecture and decoration very seriously. He never used new materials and specified only those that were used originally. There was a lack of pretense, a simple dedication to what the house was meant to be."

The archival photographs of the 1920s house reveal how thoroughly Marino revised it. A building that was so perfectly proportioned outside was in fact uneven inside: The moldings were neither consistent nor robust, and the furniture was so mixed that no room had a through-line beyond a matched pair of fauteuils. "We found it was a little poor in the detailing, a little flat," he says.

"An obligation came with the property because it was an icon that stood for civility and gentility."

First the architect updated the floor plan. He reconfigured the kitchen and consolidated the warren of bedrooms upstairs into a cogent whole, with more space for the master suite. He and George Restrepo, the architect in charge, also added a vaulted breakfast pavilion that resembles a domed tempietto and hyphenated the garage and the main house with an enclosed arcade that forms one side of the forecourt. Bill Booziotis of Dallas was the architect of record.

Inside, he created a perfection that never quite existed the first time around. He designed elegant wrought-iron-and bronze railings for the staircase and completely rethought the decorative moldings. "We added thin-lined molding in all the rooms, giving it scale with the overlay of a grid," he says.

Marino extended this rigor into the decorative arts, bridging the architecture and art with a link that is often missing in architect-designed houses. In the dining room, the beautifully crafted, lithe 19th-century Russian candelabrum and chandelier punctuate the otherwise light room. The chairs, too, are Russian, but unusual for being taut, straight and disciplined.

Marino, who studied as a painter, summoned a subdued palette inspired by the shades in the Indiana limestone façade. "It was an exercise in restraint," he says. He also kept the furniture light, with just one or two important antiques that establish character, a level of quality, and tone in rooms that are mostly monochromatic, varied only by shades. "I think that the design avoids any possible stuffiness—it reflects tradition but isn't religious about it," says Marcus.

Despite the size and complexity of the 15,000-square-foot, 21-room house, Marino achieves an almost Mozartian clarity by fitting all the parts within a well-tempered whole, as though in orchestral agreement. The limpid clarity brings out fragile but transcendent moments, whether the simple linen draperies in the master bath, the faint stenciling shimmering in border panels or brass accents on furniture that seem to flare in the space like a match, glowing against the paleness. Works by Brice Marden, Cy Twombly and Henri Matisse seem to vibrate off the walls into space. "The burst of color is not in the decoration, it's in the art," Marino says.

With signature restraint, Marino quieted the house visually so subtleties emerge, even the subtleties of the wilder kind raging in the tableau over the living room sofa. "People are surprised to see the Mitchell," says Marcus. "Her use of color and her glimpse of a deeper order earn the attention of everyone who walks in. It's just what the living room requires. That painting assures us that the room, and this house, are alive."

Use of this site constitutes acceptance of our User Agreement (effective 1/2/2014) and Privacy Policy (effective 1/2/2014). Architectural Digest may earn a portion of sales from products that are purchased through our site as part of our Affiliate Partnerships with retailers. Your California Privacy Rights (effective 1/2/2014). The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Condé Nast.